跟我一起学openGL-第一个三角形

来源：互联网发布：天津大学软件下载编辑：程序博客网时间：2024/05/22 02:02
上一篇讲述了OpenGL相关的基本概念，下面开始通过实例描述opengl的使用。
triangle.cpp  1 #include <GL/glew.h>                                                                                                                                                                                       2 #include <GL/freeglut.h>  3 #include <iostream>  4   5 #define BUFFER_OFFSET(x) ((const void*) (x))  6   7 enum VAO_IDs {Triangles, NumVAOs};  8 enum Buffer_IDs {ArrayBuffer, NumBuffers};  9 enum Attrib_IDs {vPosition = 0}; 10  11 GLuint VAOs[NumVAOs]; 12 GLuint Buffers[NumBuffers]; 13 GLuint program; 14  15 const GLchar* vertex_shader = "#version 430 core \n" 16                                 "layout(location = 0)\n" 17                                 "in vec4 vPosition;\n" 18                                 "void main()\n" 19                                 "{\n" 20                                 "gl_Position = vPosition;\n" 21                                 "}\n"; 22  23 const GLchar* fragment_shader = "#version 430 core \n" 24                                 "uniform vec4 color;\n" 25                                 "out vec4 fColor;\n" 26                                 "void main()\n" 27                                 "{\n" 28                                 "fColor = color;\n" 29                                 "}\n"; 30 void init_shader() 31 { 32         // vertex shader 33         GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER); 34         glShaderSource(vertexShader, 1, &vertex_shader, NULL); 35         glCompileShader(vertexShader); 36         // check vertex shader compiling status 37         GLint compiled; 38         GLchar log[256]; 39         glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &compiled); 40         if (!compiled) 41         { 42                 glGetShaderInfoLog(vertexShader, 256, NULL, log); 43                 std::cerr << "vertex shader compile failed" << log << std::endl; 44         } 45  46         // fragment shader 47         GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER); 48         glShaderSource(fragmentShader, 1, &fragment_shader, NULL); 49         glCompileShader(fragmentShader); 50         // check fragment shader compiling status 51         glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &compiled); 52         if (!compiled) 53         { 54                 glGetShaderInfoLog(fragmentShader, 256, NULL, log); 55                 std::cerr << "fragment shader compile failed" << log << std::endl; 56 } 57          58         // link shaders 59         program = glCreateProgram(); 60         glAttachShader(program, vertexShader); 61         glAttachShader(program, fragmentShader); 62         glLinkProgram(program); 63         //check link status 64         GLint linked; 65         glGetProgramiv(program, GL_LINK_STATUS, &linked); 66         if (!linked) 67         { 68                 glGetProgramInfoLog(program, 256, NULL, log); 69                 std::cerr << "shader linking failed" << log << std::endl; 70         } 71         // delete shader 72         glDeleteShader(vertexShader); 73         glDeleteShader(fragmentShader); 74 } 75  76 void init_data() 77 { 78         glClearColor(1, 1, 1, 0); 79         glClear(GL_COLOR_BUFFER_BIT);                                                                                                                                                                     80          81         glGenVertexArrays(NumVAOs, VAOs); 82         glBindVertexArray(VAOs[Triangles]); 83          84         GLfloat vertices[3][2] = { 85         { -0.8, -0.9 }, 86         { 0.8, -0.9 }, 87         { 0, 0.9 }, 88         }; 89  90         glGenBuffers(NumBuffers, Buffers); 91         glBindBuffer(GL_ARRAY_BUFFER, Buffers[ArrayBuffer]); 92         glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW); 93          94         glUseProgram(program); 95         // control fragment color 96         GLint loc = glGetUniformLocation(program, "color"); 97         glUniform4f(loc, 1.0f, 0.0f, 0.0f, 1.0f); 98         glVertexAttribPointer(vPosition, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0)); 99         glEnableVertexAttribArray(vPosition);100         101 }102 103 void display()104 {105         glClear(GL_COLOR_BUFFER_BIT);106 107         glBindVertexArray(VAOs[Triangles]);108         glDrawArrays(GL_TRIANGLES, 0, 3);109         glFlush();110 }111 112 int main(int argc, char* argv[])113 {114         glutInit(&argc, argv);115         glutInitDisplayMode(GLUT_RGBA);116         glutInitWindowSize(300 ,300);117         glutInitWindowPosition(100, 100);118         glutCreateWindow("Learn opengl: first triangle");119         120         glewExperimental = GL_TRUE;121         if(glewInit())122         {123                 std::cout << "Unable to Initialize" << std::endl;124                 exit(1);125         }126         init_shader();127         init_data();128         glutDisplayFunc(display);129         glutMainLoop();130 }
在Ubuntu上运行： g++ triangle.cpp -lGL -lGLU -lglut -lGLEW
即可得到下图所示的三角形：
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